Restoring Well Integrity: The Innovative Design of Thermally Activated Resin in a Sour Environment

Abstract

AbstractLoss of Well Integrity introduces the risk of uncontrolled release of formation and well fluids throughout the lifecycle of well. In a Southern Iraq field, one of the wells presented a rather unique challenge that when testing the production liner to 3000 psi, the pressure immediately dropped, and therefore, the integrity of the entire well was compromised. Pressure testing confirmed that the leak was through a liner coupling and USIT log showed that there was almost no cement bond behind the liner in the leak zone. The challenge was to find a safe and cost-effective solution to isolate and repair the hair-line leak, but also to find a solution that caters to the sour environment of the field itself, and that can last for the production lifespan of the well. A tailor-made thermally activated resin was designed in the lab to build a high compressive strength and durability and was not prone to cracking as the target treatment interval would be subjected to a pressure test as part of the conformance analysis.Conventional approaches to repair this type of leaks, such as microfine cement, are prone to deterioration and cracking over time by which well integrity is compromised. Comparing mechanical barriers such as casing patches or straddle packers were considered as backup solutions as they interfered with production requirements. Downhole Circulating temperature was carefully modeled to avoid premature setting while pumping or delayed gelation of resin once exposed to bottom hole static temperatures. The pill was then squeezed into the leak path utilizing the Bradenhead methodology and the squeeze pressure was maintained throughout the duration of the gel time of the engineered design and the plug was then allowed to fully cure. Once cured, the plug was tagged where expected and milled down to just above the bridge plug. The target treatment interval was then subjected to multiple successful pressure tests confirming the restoration of well integrity.